Method and apparatus for laying pipe in deep water



May 19, v1970 p. L MGLALLEN, JR

METHOD AND APPARATUS FOR LAYING PIP IN DEEP WATER Filed May16, 1968 INVENTOR. DEWITT L. MCLALLEN, JR.,

ATTO

avoided.

United States Patent Oihce 3,512,367 Patented May 19, 1970 Inf. cl. B636` J/ao U.s. cl. 61-7z.3 1s claims ,ABSTRACT F THE DISCLOSURE vvvPipe is laid in deep water by unreeling a continuous length of pipe from a reel on Water bottom in which a free end of the pipe is attached to a selected location and the reel is moved away from the 'selected location such as by towing from water surface.

i BACKGROUND OF THE INVENTION lField of the invention n The present invention is directed to laying pipe in deep water. More particularly, the invention is concerned with laying pipe in deep water :from a reel. In its more specific aspects, the invention is concerned with laying pipe in deep water from a reel while avoiding tension and bending stress. v

`Description of the prior art Offshore pipe lines are conveniently laid from floating vessels or-barges; the pipe may be connected by joint and lowered progressively to ocean tiooras the lay vessel moves forward and the pipe may be unspooled from a continuous reel of pipe, and pipe up to 8 in diameter has been spooled. The problem with either technique while laying pip in( deep water is the tendency of the pipe toV buckle due toits own unsupported weight at the point where it leaves the stern of the lay barge. This problem has been coped within the prior art by use of long Stingers or chutes at mize the angle of departure and the resulting pipe stress. Buoyant chambers have also been used to support the pipe between the barge and the ocean floor. With respect to laying pipe frompipe reels spool tension 'has been maintaind on the pipe as it is unreeled to reduce the bending stress toan acceptable level; tension may be maintained by winch and anchor systems oit the bow of the barge.

As 4water depth increases the amount of the unsupported pipe between the barge and water bottom increases, thus any other desirable or selected location. The reel is then moved on water bottom away from the selected location thereby unreeling the pipe and laying it on water bottom. This pipe laying technique reduces bending stress in the pipe toy a minimum and is insensitive to water depth. The spooled pipe is unreeled from a submerged position on or adjacent to or near the water bottom and thus the only tension required is that necessary to unreel and straighten the pipe. The reel may be moved on 'water bottom by towing it from water surface. The reel may be supported on or adjacent water bottom by providing controlled buoyancy such that the reel is maintained adjacent water bottom; or the reel may be mounted or supported on a frame member to which a towing cable or line is attached which extends to a powered vessel at water surface. As the pipe is unreeled it may connect the selected location to an accessible location which may be a platform or vessel in the water or it may extend to the shore.

The present invention may also be briefly summarized as involving apparatus comprising a supporting member adapted to be moved on or adjacent water bottom having a pipe reel mounted thereon and a continuous length of the pipe reeled on the pipe reel with the continuous length of the pipe having a free end adapted to be connected to a selected location. Means are provided for moving the supported member along water bottom. The apparatus also comprises straightening means for straightening the pipe as it is unreeled and may include buoyancy means which may be adjustable or at least a portion thereof-releasable.

`BRIEF DESCRIPTION OF THE DRAWING The present invention will be further described and illustrated by reference to the drawings in which:

FIG. 1 illustrates one embodiment of the present in vention; and

FIG. 2 illustrates another embodiment.

DESCRIPTION OF THE PREFERRED MODE AND EMBODIMENT 4o the stern of the barge or at the side of the barge to minig increasing bending stress. Laying.l pipe in water as deep asv 1000 feetor more provides substantial bending stresses which must be offset by use of longer Stingers, more buoyancy `and increasing pipe tension. However, the practical size of st ingers or chutes is exceeded when they become too large and cumbersome and the available tension is limited by anchor holding capabilities. The foregoing problems effectively limit the water depth of current pipe laying methods. In accordance with the present invention,VV the 'problems are substantially eliminated or Sp'eciicv prior 'art considered with respect to this inventionfinclude' the following listed U.S. Pats.: Re. 20,665,

SUMMARY OF THE INVENTION The present invention'may be briey described and y Referring now to the drawings` and particularly to FIG. l, numeral 11 designates a body of Water having surface 12 and a water bottom 13; oating on the surface 12 is a powered vessel 14 such Yas a tug and arranged on or adjacent water bottom is a pipe reel 15 containing a continuous length of pipe reeled thereon, the free end 16 of which is attached to a wellhead 17 onwater bottom 13. The pipe reel is mounted on a center axle 18 which in turn is surrounded by a spaced wall member 19 which defines a buoyant chamber 20. The wall member, 19 forms the reel 15 on which the pipe is reeled. The buoyant chamber 20 together withvreleasable buoyancy means V21 which may be attached to the pipe reel 15 by exible member 22 such as a cable, line, chain, or tubular member provides only suicient buoyancy to maintainthe pipe reel 15 at or adjacent water bottom 13. Connected to the pipe reel 15 by frame member 23 are pairs of straightening wheels 14 between which the pipe travels as it isv unspooled from the. reel 15. The reel 15 maybe connected to the vessel 14 by a tow cable 25 which causes the pipe to vunreel in the direction indicated by thearrows. Alternately and perhaps preferably, as shown in FIG. 2, the reel 15 may Ibe mounted on a frame member 26 which in turn is supported by a supporting member or skid frame member 27 to which is attached toW cable 25a by means 28 and which likewise extends t0 and is connected with powered vessel 14.

As the powered vessel 14 moves in the direction of the arrows, the pipe is unreeled from the reel 15 and is laid on Water 13 avoiding the problems of the prior art, Rather than employing a powered vessel at the water surface 12, a submarine may be used or the reel 15 or the frame'27 may be provided with power or propelling means for'moving the reel along water bottom.

Thus, in accordance with the present invention, a method andapparatus are provided employing a submersible pipe reeL or drum vhaving integral buoyancy and releasable or adjustable buoyancyyln operation the reel rotates around a center shaft or axle 18 and the Whole assembly may be Vfree or mounted on a fname; where the assembly is free, the skid frame member 27 and frame 26 would'ibe omitted. The pipe is originally spooled on the reel and the reel contains a buoyant chamber 20 and the buoyant chamber 20 may be included in or attached to skid frame '27. The buoyancy is slightly less than the weight of the reel and'skid assembly less the weight oftthe pipe.Y Attached to the center axle and skid frame is a set of straightening wheels to remove the curvature from the pipe.V Also as shown in the drawing, attached to the center axle and skid frameis at least one and'preferably a plurality of releasable buoyant chambers 21 prcviding buoyancy equal to the weight of 4the spool pipe. Alternatively, a controlled buoyant chamber may be provided permitting selective oating or releasing to vary the buoyancy of the buoyant chamber 20, thereby omitting buoyancyjmeans 21. Thus, Vthe entire assembly has a slightly negative buoyancy.

InV laying pipe using the present invention, the spool with the spooled pipe on it is moved to the work site by barge or it may be floated to the work site. The reel assembly is then lowered :or submerged with tow lines attached negar the starting point which may be a platform, a vessel, an underwater welll, or an anchor pipe, piling, and the like. The free end of the pipe is attached tolrthe starting point or selected location Vusing divers or remote connecting means. The towed vessel is then moved away from the selected location in the desired direction towing the cable to lunreel and straighten the pipe as the by a hoisting mechanism attached to the buoyancy charnber. The procedure may be repeated as desired or necessary until the pipe is brought to an accessible iocation which may be a vessel, a platform or `the shore or any other location accessible from water surface or land.

Thus, the present invention provides? new and unobviousresults and eliminates problems which have plagued theindustry"in laying pipe inV deep water from 100 t0 5000 feet. Of course. the invention is riot to be limited to any particuiar water depth and it may be applied in waters of'greater or lesser depths than those given. The invention isg'therefore, of considerable advantage and utility.VY YThe nature and objects of the present invention having been completely describedfand illustrated and the best mode and embodiment contemplated set forth what I Wish to claim asnew and useful and secure by Letters Patent is: Y'

1. A method for laying pipe in deep water which comprises: Y

supporting a submerged reel ofY pipe having a free end on water bottom; j attaching said free end to a selected location on water bottom; and i moving saidreel on said water bottom away from said selected location and therebyunreeling said pipe and laying it on said water bottom. 2. YA method in accordance with claim 1 in which the Vreel is moved on water bottom by towing it from water surface.

` selected location is a Ywellhead on water bottom.

4. A method in accordance with claim 1 in which the pipe is straightened as it is unreeled.

5. A method in accordance with claim 1 in which the unreeled pipe connects the selected location With'an -accessible location. e 'i 6. A method in accordance with claim S` in which the accessible location is at leastadjacent water surface. e

7. A method in.V accordance With claim 1 in which.'V i (a) the reel is moved 'on vwater bottom Joy towing it from water surface;

(b) the selected locationv is a wellhead tom; and v Y (c) the pipe :is straightened as it is unreeled.

8. A methodiin accordance with claim7 'in' whiehthe unreeled pipe connects Vthe selected location with a location accessible from water surface. f

9. A method in accordance with claim-7 in whichthe unreeled pipe connectsiof-an accessible'location on land.

102 A method in accordance with claim 1 in which the reel is buoyantly supported. e v

11. Apparatus for layirig pipe on water bottom which comprises: v -i a supporting member on Water bottom;

buoyancy Vmeans on said supporting' member;v

means foradjusting the lbuoyancy of v said buoyancy Va pipev reel having a'continuous length of'pipe'reeled thereon and mounted on said supporting member, said pipe having a free end adapted to be connected to a selected location on waterbottom; andmeans'attached Yto said supporting member for moving 1i said supporting member alongwater bottom.

12. Apparatus in accordance with claim 11 vin which means Yarranged' adjacent said reel isl providedz'for straightening said pipe as it is unreeled. I i v 5' 13. Apparatus in accordance with claim 11 in which said apparatus is provided with coaxial buoyancy means.

. 14. Apparatus in accordance with claim 1 inwhich the moving means comprises a flexible means extending from said supporting means to a powered vessel on water surface. Y e

, 15. vApparatus in accordance with claim 11 in' which the supporting means is coaxial with the reel. y 16. Apparatus in accordance with claim 11 in which the supporting means comprises a skid member..

17. Apparatus in accordance with claimll in which thebuoyancy means comprises a plurality of releasable buoyancy means. i y

18. Apparatus for laying pipeon water bottom which comprises: g a pipe reelprovided with a coaxial axle; e

Ywall means forming a buoyant chamber mounted be.-

tween said reel and axle; Y i

a continuous length of pipe having on said reel; releasable buoyancy means attached to said reelgfand means formoving s aid reel along water bottom. n

References -Cited f UNITED s rATEs PATENTS `f on waterebotafree endiarran-ged Wakefield 61;72.3

FOREIGN PATENTS '2,884 `12/1858 Great Britain.` Y

JACOB SHAPIRO, Primary Examiner 

